A batch-type substrate processing apparatus capable of performing a film forming process or the like on a plurality of substrates while supporting the substrates on a substrate support in multiple stages has been known.
As the batch-type substrate processing apparatus, there has been known an apparatus including an inner tube in which the substrates are accommodated, an outer tube surrounding the inner tube, a gas exhaust port installed on a sidewall of the inner tube, and an exhaust unit for exhausting a space interposed between the inner tube and the outer tube. In this apparatus, an exhaust balance is adjusted by gradually narrowing the opening width of the gas exhaust port as it is closer to the exhaust unit, so that the flow velocity of a gas supplied to the surfaces of the substrates can be uniform among the substrates.
However, in the aforementioned technique, since the opening shape of the gas exhaust port is determined for each substrate processing apparatus, there may be a case that the desired inter-plane uniformity is not obtained depending on a change in processing conditions or number of substrates to be processed. This is because the exhaust balance cannot be adjusted for each processing condition or the number of substrates to be processed.